The present invention relates to a device and method for disinfecting stored food, and more particularly, to an ultraviolet light source for disinfecting food stored in a refrigerator.
Contamination of a food supply by bacteria and other micro-organisms is a problem which has always affected mankind. Today, with the advent of mass handling and shipping of food products worldwide, the problem is more prevalent than ever. Current United States Food and Drug Administration (USFDA) estimates are that one third of the entire United States population each year will become ill due to ingestion of a food born bacteria. These numbers are appalling in a technologically advanced world that is coming into the 21st century.
Ultraviolet (UV) light has long been known for over 150 years to have germicidal properties capable of destroying bacteria, mold, yeast and viruses. UV light was one of the earliest utilized methods of disinfecting. However, its use has been discontinued because of the advent of chlorinating and ozonation disinfecting methods. The strategic advantage of UV light over these methods is that it presents an excellent alternative to chemical treatments without the concerns of toxic chemical byproducts.
Ultraviolet light having germicidal properties is centered about a wavelength of 253.7 nanometers on the electromagnetic spectrum, below the UV wavelengths responsible for suntanning, and above the X-ray portion of the spectrum. These germicidal wavelengths are emitted by the sun, but are filtered out by the Earth's ozone layer before reaching the surface.
Ultraviolet light treatment is unique in its mode of action in that it does not kill the target organism. Instead the UV light alters the target organism's cell DNA so that the target organism is sterilized. This serves to inactivate the target organism so that it cannot proliferate and cause disease. Ultraviolet light has the additional advantage of adding nothing to the exposed foods, an is easily absorbed by both solids and liquids. Effective sterilization is achieved by simply exposing the food products to the a high-energy ultraviolet light source.
A lamp emitting ultraviolet light is quite similar to a standard florescent tube lamp shown at 10 in FIG. 1 which has been used as an efficient light source for many years. The standard florescent tube 10 shown in FIG. 1 comprises an outer tube of glass 12 which is transparent to light in the visible spectrum 14, and coated on an inner surface with phosphor 16. When electrical current is supplied to the florescent lamp 10 through connectors 18a and 18b, the flow of current through a cathode element 20 triggers initiates a flow of electrons 22 towards an oppositely disposed anode clement (not shown). Disposed within the glass tube 12 are mercury atoms 24, which when struck by a flowing electron 22, emit ultraviolet radiation as at 26. Interaction between the ultraviolet radiation 26 and the phosphor coating 16 on the glass tube 12 produces light in the visible spectrum which passes through the glass tube 12. The main difference between the florescent tube lamp of FIG. 1 and an ultraviolet tube lamp is the lack of a phosphor coating on the inner surface of the ultraviolet tube lamp, and the use of a special type of glass to which is transparent to ultraviolet light frequencies emitted by the mercury atoms.